The present invention relates to a closure element and to a closure element assembly of a slide closure for use in liquid melt containers.
Basically two systems are known and customary for the exchangeable installation of fireproof or refractory plates, for example stationary bottom plates or movable side plates, of slide closures for use in metallurgical installations, such as metallurgical melting crucibles, which are subject to high wear. The first known system is to employ mortar to position the refractory plate directly in a metal support frame, such as a module frame. This refractory mortar is broken out when it is necessary to exchange the refractory plate. The second known system is to embed the refractory plate in a metallic sheath or jacket, whereby the plate unit including the refractory plate and metallic sheath is then positioned within a support frame without the use of mortar. The present invention is specifically directed to improvements of this second type of system, i.e. such system including a metallic sheath.
The fundamental purpose of a metallic sheath of this type is to provide the fireproof or refractory plate with a solid consistency, i.e. to hold the plate together, when, during the operation of the slide closure, cracks occur in the refractory plate. The formation of such cracks is practically unavoidable, given the extremely high thermal and mechanical stresses involved. Such cracks would have serious consequences if the resultant fragments of the refractory plate are allowed to spread apart or to shift relative to each other during the actuation of the slide closure. In order to safely prevent such occurrence, the metallic sheath should include a bottom portion as well as an edge or rim portion which embraces the periphery of the refractory plate. That is, the mere provision of a metallic strap placed around the edge of the plate in a hoop-like fashion would generally not be considered sufficient.
However, prior art arrangements of this type, i.e. including a refractory plate, a metallic sheath and a metal support frame, involve certain disadvantages which have been inherent. Thus, it is difficult to connect the refractory plate and the metallic sheath with the necessary precision by mass production techniques. In particular, the metallic sheath bottom portion must be very precisely aligned with the opposite surface of the refractory plate, i.e. that surface thereof which forms the sliding surface of the closure element, so that the necessary tightness between the refractory plate and another refractory plate of the slide closure is ensured during operation of the slide closure, and to ensure that the sliding plate does not get stuck during operation. However, any existing deviations in dimensions between the refractory plate and the metallic sheath can only be imperfectly compensated for by the mortar layer interposed therebetween. This is due to the fact that the mortar is subject to a certain degree of shrinkage during the drying or setting process, such shrinking not always being the same. Therefore, proper positioning and the achievement of parallel plane surfaces of the sliding surface of the refractory plate and the bottom portion of the metallic sheath can be achieved only by means of complicated and expensive supplemental assembly operations. Additionally, the mortar layer itself will not always provide a completely safe base for the refractory plate or its fragments due to pressing of the refractory plate during operation of the slide closure. Thus, local differences can exist in the amount of compression to which the mortar is subjected, and the mortar can thus sometimes become heated to such an extent during operation that it becomes soft, thereby enabling variations in the relative position of the refractory plate and the metallic sheath.